The invention relates to a method of manufacturing a motor vehicle. In principle, in extreme cases, motor vehicles can be made up completely of individual parts or put together from prefabricated parts. The conventional modern method of manufacturing motor vehicles is a mixed system.
Components and sub-assemblies prefabricated to a varying extent are inserted into opened, painted bodies. The disadvantage of this is that sensitive painted bodies may be damaged by the wide variety of far-reaching assembly work. Damage to the outer skin during assembly will involve expensive after-treatment post final assembly.. The supply and assembly of large parts is complicated and, since it is often difficult to automate, has to be manually performed under adverse physiological conditions. Assembly of smaller parts increases the number of assembly operations on site, increasing the number of operators. These operators can get in one another's way and lengthen the assembly time. Standardization and model flexibility are difficult to combine.
As is known, economic advantages can be obtained if the minimum number of pre-fitted sub-assemblies are used in the manufacture of complex engineering products. Recent manufacturing concepts, therefore, are based on prefabricating a vehicle in individual modules of maximum size. The individual modules can be completed separately. After being manufactured, optionally at different workplaces, they are brought on the conveyor belt for final assembly of the vehicle.
The manual by Horst Pippert "Karosserietechnik", 2nd edition, Wucrzburg: Vogel Buchverlag 1993, discloses various modular construction methods for rationalizing the assembly of motor vehicles.
In the sub-frame method of construction, the sub-frames receive both the chassis and the drive. They are pre- assembled with these units and screwed to the self-supporting body via Silentblock-type rubber-metal connections.
It is also known, for example, to insert the entire dashboard, including the cockpit and pedals in one module, into the front part of the semifinished body and stick or screw it to the floor group.
In another embodiment the floor element has a module with ready-mounted cockpit, pedal supports and seats, can be inserted from beneath and stuck in the body bearing structure.
It is also known to separate the front region from the roof and the floor group. By means of this horizontal division of the vehicle, the floor group can easily be equipped and, more especially, the drive block can easily be fitted before final assembly.
A division into front and rear parts results in a vertically divided body. In this case, a closed, rigid passenger compartment in the middle of the vehicle is connected to separately-prepared front and rear parts in steel frame construction.
All the different methods are based on the problem of prefabricating maximum-sized units. To a varying extent, however, they all have the disadvantage that in they mostly optimize only one requirement, e.g. ease of assembly, but require compensating far-reaching structural changes or design changes.
Frequently it is necessary to abandon the economic method of constructing the self-supporting body from pressed parts, or new materials have to be used without a convincing amount of advantage.
WO 92/07749 discloses a method of assembling a motor vehicle, where a front structure after completion is connected to a completed rear structure. The dividing line of the body extends centrally via the roof region. A disadvantage of the known method is that, owing to the required stability, it is very complicated to connect the two main parts of the body. In the case of a self-supporting body the roof region is load-bearing. If the front structure is joined to the rear structure centrally in the roof region, the very thin sheet metal cannot bear loads, and consequently the floor group, which is similarly divided, has to be suitably reinforced. Such reinforcement considerably increases the weight.
JP-A-6-8851 discloses a concept where the body is not equatorially divided, but the vehicle comprises a number of components. The floor group like the body, which is mounted on the floor group, comprises two parts. The method disclosed in the citation emphasizes the importance of the skeleton and is very close to the frame construction of cars in earlier periods. It shows the need for strong profile and auxiliary frames.